It has been established by tests that application of a lubricant, usually a petroleum base, to those surfaces of the wheels of a railroad car frictionally engaged by a railroad car retarder when the car is slowed down thereby, will reduce or eliminate the tendency of the car wheels to squeal. Since the squeal noise often made by the car wheels as the car is being retarded is far higher in noise level, measured in decibels on the A scale (dbA), than is allowed by the Occupational Safety Hazard Agency (O.S.H.A.) standards and noise pollution limits established by many communities, means for controlling noise is vital to railroads, especially for yard classification operations.
At present, the more commonly used lubricant is a water soluble oil diluted with water and anti-freeze generally mixed in a ratio of one part oil to ten parts dilutant. Apparatus is provided for spraying the mixture onto the car wheels either before the railroad car enters the retarder or while it is moving therethrough. This method presents inherent undesirable disadvantages, namely: (a) the spray cannot be sufficiently controlled for preventing such spray from spreading over areas of the wheel not needed to be lubricated; (b) lubricating fluid must contain such dilutants as anti-freeze and fuel oil in order to prevent freezing thereof in sub-freezing temperatures; (c) pressure operated spraying apparatus for spraying the fluid along with sumps and sump pump systems for recovering and recirculating the lubricating fluid must be provided; (d) fire hazards presented by flammable lubricating liquids; (e) slippery conditions and surfaces prevailing in the retarder area due to the spray; and (f) the many maintenance problems attendant with a spraying system, fluid levels, pumps, filters, sumps, etc.